compareVersion() is really simply a wrapper for PHP's version_compare, though it contains some minor logic to accommodate what we termed "Preview Release" versions prior to 1.8, but which were, in fact, alpha versions. (The logic does a simple regular expression to translate "pr" to "a" in the version string.) If we did not have those versions haunting us, we would have no need for the method, to be honest.

As long as your version numbers follow those that version_compare() understands, I really see no need to extend Zend_Version; simply create a namespace-level constant or a class constant, and feed it to version_compare().